Title page for ETD etd-01152012-183124

Water Quality Dynamics of Low-Gradient, Headwater Streams in a Timber-Industry Dominated Watershed in Louisiana

Degree

Master of Science (M.S.)

Department

Renewable Natural Resources

Advisory Committee

Advisor Name

Title

Xu, Jun

Committee Chair

Gambrell, Robert

Committee Member

Kelso, William

Committee Member

Keywords

non-point source pollution

headwater streams

forestry bmps

water quality

Date of Defense

2011-12-12

Availability

unrestricted

Abstract

Timber harvesting can degrade the quality of adjacent water bodies, an important concern for Louisiana, nearly 50% of which is forested, and in which the forest industry is the second-largest manufacturing employer. To protect valuable freshwater resources in Louisiana, a manual of best management practices (BMPs) was published in 2000 describing techniques for limiting forestry-caused water quality degradation. While these BMPs are widely implemented, their effectiveness in protecting water quality is largely unknown. To determine the effectiveness of these BMPs, this thesis research conducted three studies to address timber harvest BMP effectiveness on protection of stream dissolved oxygen, metabolism, and carbon, nitrogen, and phosphorus runoff in a low-gradient watershed, Flat Creek, in north-central Louisiana, USA. The first two studies were carried out on a 2nd-order stream adjacent to a loblolly pine stand from 2006 to 2010 that was harvested in the summer of 2007. Dissolved oxygen (DO), water temperature, and stream depth were recorded at 15-minute intervals at a reference site upstream and a site downstream of the harvested area. Using diurnal DO change and an open-system, single-station method at each site, we quantified rates of net productivity (NP), gross primary productivity (GPP), community respiration (CR), and GPP/CR ratios. The third study was conducted at nine sites across the Flat Creek watershed, from 1st-order to 3rd-order streams, for analyses of immediate downstream and watershed-scale changes to stream carbon, nitrogen, and phosphorus concentrations from three timber harvests conducted in 2007. There were no statistically significant changes to any measured carbon, nitrogen, or phosphorus species at either the forest stand scale, or at the watershed scale. Overall, results from this research suggest that Louisiana’s current BMPs were effective at limiting water quality degradation.